The Kindle battery charging is under software control (per: GM) -
So if the software is "bricked" you can't be certain it is being charged.

The Kindle 3G modem/radio is under software control -
If the software is "bricked" you can't be certain the transmitter is off.
The 3G transmitter pulls 2 amps during each "burst" transmission, so if it is on and "yelling for help" - your battery will not last very long.

The k3 is easy to open with a jeweler's screwdriver -- no easy to damage "slide-snaps" and no glue. You could open it and remove the 3G modem from its socket before trying to charge the kindle battery.